Studies on processes and factors to regulate wetland ecosystem.

外来物种鲤鱼(Cyprinus Carpio)和红沼泽小龙虾(Procambarus Clarkii)作为关键物种和外来生态系统工程师改变了群落和生态系统。我们考察了不同密度的鲤鱼和小龙虾是否有不同的影响，并比较了它们的密度依赖效应。通过围隔实验，研究了鲤鱼和小龙虾密度与水质、浮游植物、营养盐动态、沉水植物(种子库育苗)、浮游动物、底栖大型无脊椎动物和沉积物有机质的关系。我们假设密度与响应变量之间的关系是：(I)线性或(Ii)非线性(指数饱和曲线)。鲤鱼和小龙虾都增加了悬浮固体(SS)、无机悬浮固体(ISS)和叶绿素a(Chla)，改变了营养动态，减少了沉水植物和底栖大型无脊椎动物，尽管只有鲤鱼影响浮游动物和…沉积物有机质较多。然而，鲤鱼和小龙虾表现出不同的密度依赖效应。SS、ISS、Chl.a、NH4-N与摇蚊对鲤鱼密度的响应呈非线性关系，表明鲤鱼在低密度下对这些变量的影响很大。相比之下，小龙虾对沉水植物的负面影响较大，且呈非线性关系。鲤鱼和小龙虾对这些变量的影响可能是由于生物扰动、排泄和捕食的共同作用，表明生态系统工程可能对其他群落成员产生了显著影响。此外，它们影响的差异与功能独特性有关。我们还证明，引入鲤鱼和小龙虾等外来生态工程可能会引发从以大型植物为主的清水状态向以浮游植物为主的混浊状态的转变。我们的结果为根除鲤鱼和小龙虾的战略提供了重要的启示。虽然尽可能地消灭这些物种是保护和恢复当地生物多样性和生态系统的最佳管理做法，但我们建议优先考虑消除小龙虾以保护大型植物。较少

Exotic species common carp (Cyprinus carpio) and red swamp crayfish (Procambarus clarkii) modify communities and ecosystems as keystone species and exotic ecosystem engineers. We examined whether different densities of carp and crayfish have different impacts, and compared their density-dependent effects. Using an enclosure experiment, we investigated the relationships between carp or crayfish density and water quality, phytoplankton, nutrient dynamics, submerged macrophytes (the establishment of seeding from seed bank), zooplankton, benthic macroinvertebrates and sediment organic matter. We hypothesize that the relationship between density and response variable are either : (i) linear or (ii) non-liner (exponential saturated curve). Both carp and crayfish increased suspended solids (SS), inorganic suspended solids (ISS) and chlorophyll a (Chl.a), changed nutrient dynamics and decreased submerged macrophytes and benthic macroinvertebrates, although only carp affected on zooplankton and … More sediment organic matter. However, carp and crayfish showed different density-dependent effects. The relationships between SS,ISS,Chl.a,NH_4-N and Chironominae response to carp density were non-linear, indicating that carp have strong effects on these variables at even low density. In contrast, crayfish have a large negative effect on submerged macrophytes and the relationship was non-linear. The observed effects of carp and crayfish on these variables were probably due to a combination of bioturbation, excretion and predation, suggesting that ecosystem engineering may have pronounced impactson other community members. Also, differences in their impacts were related to functional uniqueness. We also demonstrate that an introduction of exotic ecosystem engineer such as carp and crayfish may trigger a shift from a clear water state with abundant macrophytes to a turbid state dominated by phytoplankton. Our results provide important implications for strategies to eradicate carp and crayfish. Although eliminating these species as much as possible is the best management practice for conservation and restoration of native biodiversity and ecosystem, we propose that it gives first priority to remove crayfish to conserve macrophytes. Less